In order to protect the skin against the harmful effects of sunlight, it is well known to provide artificial photoprotection by the topical cutaneous application of agents that prevent the action of UV in two ways:
by absorbing the energy supplied by the photons; these are standard UVA-active and/or UVB-active organic and/or mineral sunscreens;
by scattering the light using a physical sunblock, for instance titanium dioxide. “Total sunblock” creams generally contain such a product plus a chemical screening agent.
Antioxidants such as vitamin E, carotenoids or glutathione, which may be of value in reducing the effects of cellular oxidative stress, may also be provided. These agents induce active photoprotection by stimulating the natural defence systems of the skin cells against the damage induced by UV irradiation.
The use of 2-oxothiazolidine-4-carboxylic acid has already been the subject of numerous studies and patents, especially with the aim of protecting the body against various types of stress. Thus, it is known from document U.S. Pat. No. 5,208,249 (Clintec) that 2-oxothiazolidine-4-carboxylic acid and its esters are capable of stimulating glutathione synthesis in certain cells of the human body. Glutathione, which is found in all eukaryotic cells, is a tripeptide composed of the following three amino acids: glutamic acid, cysteine and glycine. Glutathione is especially known to participate in protecting cells against various types of damage, such as that caused by free radicals (U.S. Pat. No. 5,208,249) and to play a central role in the antioxidant defence systems against free radicals and toxic compounds of endogenous and exogenous origin (J. Med. Chem., 1999, Vol. 42, No. 23, pp. 4733–4740).
In addition, it is known practice from document EP 0 655 245 (Free Radical Science) to use a composition containing 2-oxothiazolidine-4-carboxylic acid or its esters to delay the ageing process in mammals, by maintaining intracellular glutathione levels at an amount that is sufficient to prevent the oxidative damage caused by free radicals on cells.
It nevertheless remains that the desire to protect the skin and other epidermal growths against oxidative and photo-oxidative stress in order to maintain or improve the appearance of an individual's skin still leads to the incessant search for novel agents that are effective for protecting the skin and other epidermal growths, the said agents moreover needing to be well metabolized and able to be formulated in compositions, especially cosmetic compositions.
A process for synthesizing a heterocyclic derivative of formula (II) has indeed been reported in the prior art (Bull. Chem. Soc. Jpn., 1964, 37 (2), pp. 242–244), but this derivative is not described as an agent for stimulating the intracellular synthesis of glutathione.
